The present invention relates to electronic equipment for patient monitoring, recording, or triggering type applications, in particular to an interface that allows sharing of ECG and/or blood-pressure signals among multiple medical devices.
During treatment of a patient, the patient may be monitored through surface electrodes attached to the patient's skin, or other sensors, such as blood-pressure sensors, contained within a catheter inserted into the patient. Frequently, multiple different medical devices will require signals from the same electrodes or sensors. For example, ECG signals from skin electrodes may be required by a patient monitoring device for displaying ECG signals, a recording device recording those signals, a mapping device locating intra-cardiac electrodes, and a respiration sensor using the electrodes (but not the signals) for respiration monitoring. Similarly, blood-pressure information from a single blood-pressure sensor may be required by different medical devices.
Ideally multiple devices could share electrodes or other sensors such as catheter blood-pressure sensors to avoid exceeding the limited number of connections that can be practically made between devices and the patient. In practice, this sharing can be difficult. Attaching multiple devices to a given electrode may unduly load the electrode, reducing the signal and increasing noise. Often, some uses of a given set of electrodes will be incompatible with other uses. For example, when an ECG monitoring system injects current into the ECG signal for impedance measurement, the injected signals may conflict or interfere with measurements made by other connected medical devices. With respect to blood-pressure sensors, it is not uncommon for different monitoring devices to apply different excitation voltages to the blood-pressure sensors and to expect blood-pressure signals in different voltage ranges.